A sexual act in which the flab of the under arm 'slaps' the scrotum of another person back and forth.
Person one: "Dude, how was that chick last night?
Persona two: "She gave me a slappyjackle in the toilet cubical, it felt amazing..."
Persona two: "She gave me a slappyjackle in the toilet cubical, it felt amazing..."
by Happy Jackle December 3, 2013
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